Investigation of nuclear criticality within a powder using coupled neutronics and thermofluids

This paper investigates the dynamics of a postulated criticality in a powder used as part of fuel processing. Numerical simulations are performed in 2D and 3D geometries in which layers of MOX, UO2 and zinc stearate (acting as a moderating lubricant) powders become supercritical. The system simulated here were initialised with a step reactivity insertion of 1$, 2$ and 5$. The coupled radiation and multiphase–multicomponent simulations showed complex dynamics with an increase of powder temperature and mixing of the moderator into the MOX.